Molecular sieves, referred to as zeolites, have found application in various hydrocarbon conversion processes, including isomerization and hydrocracking. For use in the hydrocarbon conversion processes, the catalyst compositions containing the zeolites often contain a hydrogenation/dehydrogenation component. A valuable hydrogenation/dehydrogenation component is platinum. During use in catalytic hydrocarbon conversion processes, zeolites containing the platinum hydrogenation/dehydrogenation component undergo gradual deactivation.
Deactivation of the platinum-containing zeolite catalyst compositions is attributable in part to coke deposition and in part to migration and agglomeration of the noble metal component. Coke deactivation is readily reversible by conventional oxidative regeneration, but such regeneration has little if any effect in redispersing the agglomerated noble metal, and may in fact bring about further agglomeration. Parenthetically, the extent of agglomeration can be reflected in X-ray diffraction patterns of the catalyst composition; as the platinum agglomeration increases and becomes more aggravated, the X-ray diffraction pattern reflects the increase in size of the agglomerates.
The prior art has recognized the problem of agglomeration of the Group VIII noble metal, supported on the zeolite during deactivation, and during oxygen regeneration. In recognizing the problem, the prior art has presented several alternatives for attempting to regenerate such catalysts. Exemplary of the art, directed to the problem of reactivating noble metal zeolite Y containing hydrocracking catalysts include U.S. Pat. No. 4,107,031; U.S. Pat. No. 4,139,433; U.S. Pat. No. 3,943,051; Reichle et al., "Hydrocracking Catalyst Rejuvenated", The Oil and Gas Journal, p. 137 et seq. (July 29, 1974) and Reichle et al., "New Rejuvenation Techniques extend Unicracking-JHC Catalyst Life", presented at the NPRA Annual Meeting, Spring 1974; U.S. Pat. Nos. 3,849,293 and 3,692,692. The United States patents, referred herein, providing alternatives for reactivating Group VIII noble metal containing zeolite catalyst compositions rely upon the use of ammonia treatment.